import math

x1, y1, x2, y2 = [float(line) for line in input().split()]
double_distance = math.sqrt((x2 - x1) ** 2 + (y2 - y1) ** 2)

print(double_distance)
 import math math float(line) for line in input().split() for line in input().split() line input().split() ().split () input split for line in input().split() float(line) float line x1, y1, x2, y2 = [float(line) for line in input().split()] x1 [float(line) for line in input().split()] y1 x2 y2 double_distance = math.sqrt((x2 - x1) ** 2 + (y2 - y1) ** 2) double_distance math.sqrt((x2 - x1) ** 2 + (y2 - y1) ** 2) math.sqrt math sqrt (x2 - x1) ** 2 + (y2 - y1) ** 2 (x2 - x1) ** 2 x2 - x1 x2 x1 2 (y2 - y1) ** 2 y2 - y1 y2 y1 2 print(double_distance) print double_distance y1, x2, y2 = [float(line) for line in input().split()] [float(line) for line in input().split()] y1 x2, y2 = [float(line) for line in input().split()] [float(line) for line in input().split()] x2 double_distance = math.sqrt((x2 - x1) ** 2 + (y2 - y1) ** 2) math.sqrt((x2 - x1) ** 2 + (y2 - y1) ** 2) double_distance y2 = [float(line) for line in input().split()] [float(line) for line in input().split()] y2 x1, y1, x2, y2 = [float(line) for line in input().split()] [float(line) for line in input().split()] x1
import math

x1, y1, x2, y2 = [float(line) for line in input().split()]
double_distance = math.sqrt((x2 - x1) ** 2 + (y2 - y1) ** 2)

print(double_distance)

